Emission plays an important role in engine development. In particular, engine manufactures have learned that fuel injection plays a crucial role in determining the amount of emissions that an engine produces. Traditionally, a fuel injector would only operate in one mode of operation, injecting fuel towards the side of the cylinder when the piston approached top dead center. At this point, the compressed air is hot enough to cause combustion. However, engineers have learned that injecting in dual modes during the same engine cycle may substantially reduce the amount of the emissions created during the combustion process. Specifically, it has been learned that it is desirable to inject a small amount of fuel while the piston is near bottom dead center. As the piston moves closer to top dead center position, the fuel mixes with the air, as it is being compressed, to form a relatively lean homogeneous mixture. Traditional fuel injection also occurs near top dead center and combustion occurs as a result of the temperature of the compressed air. This process is commonly referred to as homogeneously charge compression ignition (HCCI).
The prior art has attempted to create dual mode injectors; however, improvement is still necessary for more viable dual mode operation. U.S. Pat. No. 6,186,419 B1, issued to Kampman et al., discloses an injector that is capable of injecting, in different modes based upon engine operating conditions. Specifically, a sleeve is disposed around a fuel injector that is capable of impinging the fuel spray as it is injected into the cylinder. By moving the sleeve up and down, the degree of impingement can be changed. At the fully retracted position, the injector injects towards the side of the cylinder without any impingement and at the fully advanced position, the injection spray is completely impinged and directed towards the bottom of the cylinder. However, in this patent, the sleeve is moved through a rack and pinion approach, and the sleeve is not capable of quickly transitioning between multiple modes during a single engine cycle. Further, the sleeve disposed around the injection tip provides only a vertical surface of impingement which limits the flexibility of the injector and limits the ability to achieve homogenous mixtures.
In other attempts to achieve dual mode operation, engine manufacturers have placed two fuel injector nozzles into a cylinder, each operating in a different mode. The first nozzle performs the initial homogenous charge injection, directed toward the bottom of the cylinder when the piston is near bottom dead center, and the second nozzle, with different orifice angles injects in the traditional fashion when the piston is near top dead center. Unfortunately, this approach requires numerous extra components, adding cost and taking up additional packaging space.
The present invention is directed to overcome one or more of the problems set forth above.